Diamondoid-containing capacitors

ABSTRACT

Novel uses of diamondoid-containing materials in the field of microelectronics are disclosed. Embodiments include, but are not limited to, thermally conductive films in integrated circuit packaging, low-k dielectric layers in integrated circuit multilevel interconnects, thermally conductive adhesive films, thermally conductive films in thermoelectric cooling devices, passivation films for integrated circuit devices (ICs), and field emission cathodes. The diamondoids employed in the present invention may be selected from lower diamondoids, as well as the newly provided higher diamondoids, including substituted and unsubstituted diamondoids. The higher diamondoids include tetramantane, pentamantane, hexamantane, heptamantane, octamantane, nonamantane, decamantane, and undecamantane. The diamondoid-containing material may be fabricated as a diamondoid-containing polymer, a diamondoid-containing sintered ceramic, a diamondoid ceramic composite, a CVD diamondoid film, a self-assembled diamondoid film, and a diamondoid-fullerene composite.

REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. ProvisionalPatent Application No. 60/262,842 filed Jan. 19, 2001. U.S. ProvisionalPatent Application No. 60/262,842 is hereby incorporated herein byreference in its entirety. The present application also herebyincorporates by reference in its entirety U.S. Patent Application Ser.No. 60/334,939, entitled “Polymerizable Higher Diamondoid Derivatives,”by Shenggao Liu, Jeremy E. Dahl, and Robert M. Carlson, filed Dec. 4,2001, and also U.S. Provisional Patent Application Ser. No. 60/341,921,filed Dec. 18, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] Embodiments of the present invention are directed toward noveluses of both lower and higher diamondoid-containing materials in thefield of microelectronics. These embodiments include, but are notlimited to, the use of such materials as heat sinks in microelectronicspackaging, passivation films for integrated circuit devices (ICs), low-kdielectric layers in multilevel interconnects, thermally conductivefilms, including adhesive films, thermoelectric cooling devices, andfield emission cathodes.

[0004] 2. State of the Art

[0005] Carbon-containing materials offer a variety of potential uses inmicroelectronics. As an element, carbon displays a variety of differentstructures, some crystalline, some amorphous, and some having regions ofboth, but each form having a distinct and potentially useful set ofproperties.

[0006] A review of carbon's structure-property relationships has beenpresented by S. Prawer in a chapter titled “The Wonderful World ofCarbon,” in Physics of Novel Materials (World Scientific, Singapore,1999), pp. 205-234. Prawer suggests the two most important parametersthat may be used to predict the properties of a carbon-containingmaterial are, first, the ratio of sp² to sp³ bonding in a material, andsecond, microstructure, including the crystallite size of the material,i.e. the size of its individual grains.

[0007] Elemental carbon has the electronic structure 1 s ²²s²²p², wherethe outer shell 2 s and 2 p electrons have the ability to hybridizeaccording to two different schemes. The so-called sp³ hybridizationcomprises four identical a bonds arranged in a tetrahedral manner. Theso-called sp²-hybridization comprises three trigonal (as well as planar)a bonds with an unhybridized p electron occupying a π orbital in a bondoriented perpendicular to the plane of the σ bonds. At the “extremes” ofcrystalline morphology are diamond and graphite. In diamond, the carbonatoms are tetrahedrally bonded with sp³-hybridization. Graphitecomprises planar “sheets” of sp²-hybridized atoms, where the sheetsinteract weakly through perpendicularly oriented π bonds. Carbon existsin other morphologies as well, including amorphous forms called“diamond-like carbon,” and the highly symmetrical spherical androd-shaped structures called “fullerenes” and “nanotubes,” respectively.

[0008] Diamond is an exceptional material because it scores highest (orlowest, depending on one's point of view) in a number of differentcategories of properties. Not only is it the hardest material known, butit has the highest thermal conductivity of any material at roomtemperature. It displays superb optical transparency from the infraredthrough the ultraviolet, has the highest refractive index of any clearmaterial, and is an excellent electrical insulator because of its verywide bandgap. It also displays high electrical breakdown strength, andvery high electron and hole mobilities. If diamond as a microelectronicsmaterial has a flaw, it would be that while diamond may be effectivelydoped with boron to make a p-type semiconductor, efforts to implantdiamond with electron-donating elements such as phosphorus, to fabricatean n-type semiconductor, have thus far been unsuccessful.

[0009] Attempts to synthesize diamond films using chemical vapordeposition (CVD) techniques date back to about the early 1980's. Anoutcome of these efforts was the appearance of new forms of carbonlargely amorphous in nature, yet containing a high degree ofsp³-hybridized bonds, and thus displaying many of the characteristics ofdiamond. To describe such films the term “diamond-like carbon” (DLC) wascoined, although this term has no precise definition in the literature.In “The Wonderful World of Carbon,” Prawer teaches that since mostdiamond-like materials display a mixture of bonding types, theproportion of carbon atoms which are four-fold coordinated (orsp³-hybridized) is a measure of the “diamond-like” content of thematerial. Unhybridized p electrons associated with sp²-hybridizationform π bonds in these materials, where the π bonded electrons arepredominantly delocalized. This gives rise to the enhanced electricalconductivity of materials with sp² bonding, such as graphite. Incontrast, sp³-hybridization results in the extremely hard, electricallyinsulating and transparent characteristics of diamond. The hydrogencontent of a diamond-like material will be directly related to the typeof bonding it has. In diamond-like materials the bandgap gets larger asthe hydrogen content increases, and hardness often decreases. Notsurprisingly, the loss of hydrogen from a diamond-like carbon filmresults in an increase in electrical activity and the loss of otherdiamond-like properties as well.

[0010] Nonetheless, it is generally accepted that the term “diamond-likecarbon” may be used to describe two different classes of amorphouscarbon films, one denoted as “a:C—H,” because hydrogen acts to terminatedangling bonds on the surface of the film, and a second hydrogen-freeversion given the name “ta-C” because a majority of the carbon atoms aretetrahedrally coordinated with sp³-hybridization. The remaining carbonsof ta-C are surface atoms that are substantially sp²-hybridized. Ina:C—H, dangling bonds can relax to the sp² (graphitic) configuration.The role hydrogen plays in a:C—H is to prevent unterminated carbon atomsfrom relaxing to the graphite structure. The greater the sp³ content themore “diamond-like” the material is in its properties such as thermalconductivity and electrical resistance.

[0011] In his review article, Prawer states that tetrahedral amorphouscarbon (ta-C) is a random network showing short-range ordering that islimited to one or two nearest neighbors, and no long-range ordering.There may be present random carbon networks that may comprise 3, 4, 5,and 6-membered carbon rings. Typically, the maximum sp³ content of ata-C film is about 80 to 90 percent. Those carbon atoms that are sp²bonded tend to group into small clusters that prevent the formation ofdangling bonds. The properties of ta-C depend primarily on the fractionof atoms having the sp³, or diamond-like configuration. Unlike CVDdiamond, there is no hydrogen in ta-C to passivate the surface and toprevent graphite-like structures from forming. The fact that graphiteregions do not appear to form is attributed to the existence of isolatedsp² bonding pairs and to compressive stresses that build up within thebulk of the material.

[0012] The microstructure of a diamond and/or diamond-like materialfurther determines its properties, to some degree because themicrostructure influences the type of bonding content. As discussed in“Microstructure and grain boundaries of ultrananocrystalline diamondfilms” by D. M. Gruen, in Properties, Growth and Applications ofDiamond, edited by M. H. Nazaré and A. J. Neves (Inspec, London, 2001),pp. 307-312, recently efforts have been made to synthesize diamondhaving crystallite sizes in the “nano” range rather than the “micro”range, with the result that grain boundary chemistries may differdramatically from those observed in the bulk. Nanocrystalline diamondfilms have grain sizes in the three to five nanometer range, and it hasbeen reported that nearly 10 percent of the carbon atoms in ananocrystalline diamond film reside in grain boundaries.

[0013] In Gruen's chapter, the nanocrystalline diamond grain boundary isreported to be a high-energy, high angle twist grain boundary, where thecarbon atoms are largely π-bonded. There may also be sp bonded dimers,and chain segments with sp³-hybridized dangling bonds. Nanocrystallinediamond is apparently electrically conductive, and it appears that thegrain boundaries are responsible for the electrical conductivity. Theauthor states that a nanocrystalline material is essentially a new typeof diamond film whose properties are largely determined by the bondingof the carbons within grain boundaries.

[0014] Another allotrope of carbon known as the fullerenes (and theircounterparts carbon nanotubes) has been discussed by M. S. Dresslehauset al. in a chapter entitled “Nanotechnology and Carbon Materials,” inNanotechnology (Springer-Verlag, New York, 1999), pp. 285-329. Thoughdiscovered relatively recently, these materials already have a potentialrole in microelectronics applications. Fullerenes have an even number ofcarbon atoms arranged in the form of a closed hollow cage, whereincarbon-carbon bonds on the surface of the cage define a polyhedralstructure. The fullerene in the greatest abundance is the C₆₀ molecule,although C₇₀ and C₈₀ fullerenes are also possible. Each carbon atom inthe C₆₀ fullerene is trigonally bonded with sp²-hybridization to threeother carbon atoms.

[0015] C₆₀ fullerene is described by Dresslehaus as a “rolled up”graphine sheet forming a closed shell (where the term “graphine” means asingle layer of crystalline graphite). Twenty of the 32 faces on theregular truncated icosahedron are hexagons, with the remaining 12 beingpentagons. Every carbon atom in the C₆₀ fullerene sits on an equivalentlattice site, although the three bonds emanating from each atom are notequivalent. The four valence electrons of each carbon atom are involvedin covalent bonding, so that two of the three bonds on the pentagonperimeter are electron-poor single bonds, and one bond between twohexagons is an electron-rich double bond. A fullerene such as C₆₀ isfurther stabilized by the Kekulé structure of alternating single anddouble bonds around the hexagonal face.

[0016] Dresslehaus et al. further teach that, electronically, the C₆₀fullerene molecule has 60 electrons, one π electronic state for eachcarbon atom. Since the highest occupied molecular orbital is fullyoccupied and the lowest un-occupied molecular orbital is completelyempty, the C₆₀ fullerene is considered to be a semiconductor with veryhigh resistivity. Fullerene molecules exhibit weak van der Waalscohesive interactive forces toward one another when aggregated as asolid.

[0017] The following table summarizes a few of the properties ofdiamond, DLC (both ta-C and a:C—H), graphite, and fullerenes: C₆₀Property Diamond ta-C a:C-H Graphite Fullerene C-C bond length (nm)0.154 ≈0.152 0.141 pentagon: 0.146 hexagon: 0.140 Density (g/cm³)3.51 >3 0.9-2.2 2.27 1.72 Hardness (Gpa) 100 >40 <60 soft Van der WaalsThermal conductivity 2000 100-700 10 0.4 (W/mK) Bandgap (eV) 5.45 ≈30.8-4.0 metallic 1.7 Electrical resistivity >10¹⁶ 10¹⁰ 10²-10¹² 10⁻³-1>10⁸ (Ω cm) Refractive Index 2.4 2-3 1.8-2.4 — —

[0018] The data in the table is compiled from p. 290 of the Dresslehauset al. reference cited above, p. 221 of the Prawer reference citedabove, p. 891 a chapter by A. Erdemir et al. in “Tribology of Diamond,Diamond-Like Carbon, and Related Films,” in Modern Tribology Handbook,Vol. Two, B. Bhushan, Ed. (CRC Press, Boca Raton, 2001), and p. 28 of“Deposition of Diamond-Like Superhard Materials,” by W. Kulisch,(SpringerVerlag, New York, 1999).

[0019] A form of carbon not discussed extensively in the literature are“diamondoids.” Diamondoids are bridged-ring cycloalkanes that compriseadamantane, diamantane, triamantane, and the tetramers, pentamers,hexamers, heptamers, octamers, nonamers, decamers, etc., of adamantane(tricyclo[3.3.1.1^(3,7)] decane), adamantane having the stoichiometricformula C₁₀H₁₆, in which various adamantane units are face-fused to formlarger structures. These adamantane units are essentially subunits ofdiamondoids. The compounds have a “diamondoid” topology in that theircarbon atom arrangements are superimposable on a fragment of an FCC(face centered cubic) diamond lattice.

[0020] Diamondoids are highly unusual forms of carbon because while theyare hydrocarbons, with molecular sizes ranging in general from about 0.2to 20 nm (averaged in various directions), they simultaneously displaythe electronic properties of an ultrananocrystalline diamond. Ashydrocarbons they can self-assemble into a van der Waals solid, possiblyin a repeating array with each diamondoid assembling in a specificorientation. The solid results from cohesive dispersive forces betweenadjacent C—H_(x) groups, the forces more commonly seen in normalalkanes.

[0021] In diamond nanocrystallites the carbon atoms are entirelysp³-hybridized, but because of the small size of the diamondoids, only asmall fraction of the carbon atoms are bonded exclusively to othercarbon atoms. The majority have at least one hydrogen nearest neighbor.Thus, the majority of the carbon atoms of a diamondoid occupy surfacesites (or near surface sites), giving rise to electronic states that aresignificantly different energetically from bulk energy states.Accordingly, diamondoids are expected to have unusual electronicproperties.

[0022] To the inventors' knowledge, adamantane and substitutedadamantane are the only readily available diamondoids. Some diamantanes,substituted diamantanes, triamantanes, and substituted triamantanes havebeen studied, and only a single tetramantane has been synthesized. Theremaining diamondoids are provided for the first time by the inventors,and are described in their co-pending U.S. Provisional PatentApplications No. 60/262,842, filed Jan. 19, 2001; 60/300,148, filed Jun.21, 2001; 60/307,063, filed Jul. 20, 2001; 60/312,563, filed Aug. 15,2001; 60/317,546, filed Sep. 5, 2001; 60/323,883, filed Sep. 20, 2001;60/334,929, filed Dec. 4, 2001; and 60/334,938, filed Dec. 4, 2001,incorporated herein in their entirety by reference. Applicants furtherincorporate herein by reference, in their entirety, the non-provisionalapplications sharing these titles which were filed on Dec. 12, 2001. Thediamondoids that are the subject of these co-pending applications havenot been made available for study in the past, and to the inventors'knowledge they have never been used before in a microelectronicsapplication.

SUMMARY OF THE INVENTION

[0023] Embodiments of the present invention are directed toward noveluses of diamondoid-containing materials in the field ofmicroelectronics. Diamondoids are bridged-ring cycloalkanes. Theycomprise adamantane, diamantane, and triamantane, as well as thetetramers, pentamers, hexamers, heptamers, octamers, nonamers, decamers,etc., of adamantane (tricyclo[3.3.1.1^(3,7)] decane), in which variousadamantane units are face-fused to form larger structures. The compoundshave a “diamondoid” topology in that their carbon atom arrangements aresuperimposable on a fragment of an FCC diamond lattice. The presentembodiments include, but are not limited to, thermally conductive filmsin integrated circuit (IC) packaging, low-k dielectric layers inintegrated circuit multilevel interconnects, thermally conductiveadhesive films, thermally conductive films in (Peltier-based)thermoelectric cooling devices, passivation films for integrated circuitdevices, dielectric layers in SRAM and DRAM capacitors, and fieldemission cathodes, each application based upon incorporating one or morediamondoid-containing materials. The diamondoid-containing materials ofthe present invention may be fabricated as a diamondoid-containingpolymer, a diamondoid-containing sintered ceramic, a diamondoid ceramiccomposite, a CVD diamondoid film, and a self-assembled diamondoid film.Diamondoid-containing materials further include diamondoid-fullerenecomposites.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 schematically illustrates a process flow whereindiamondoids may be extracted from petroleum feedstocks, processed into auseful form, and then incorporated into a specific microelectronicsapplication;

[0025] FIGS. 2A-C illustrate exemplary polymeric materials that may befabricated from diamondoids;

[0026]FIG. 2D illustrate the variety of three-dimensional shapesavailable among the highly symmetrical 396 molecular weighthexamantanes;

[0027]FIG. 2E illustrates the variety of three-dimensional shapesavailable among enantiomers of the chiral 396 molecular weighthexamantanes;

[0028] FIGS. 2F-H illustrates the variety of carbon attachment sites ona decamantane molecule, and how attachments to different sites in apolymer may result in cross-linked materials of variable rigidity,

[0029] FIGS. 2I-K illustrate the manner in which a pentamantane may beoriented in a cross-linked polymer such that, in each case, the variousdiamond crystal lattice planes are substantially parallel;

[0030] FIGS. 2L-M illustrate an exemplary chiral polymers prepared fromenantiomers of [123] tetramantane;

[0031]FIG. 2N illustrates [1(2,3)4] pentamantane.

[0032]FIG. 3A illustrates in schematic form a process flow by whichdiamondoids may be sintered into ceramic-like materials and ceramiccomposites;

[0033]FIG. 3B illustrates in schematic form a diamondoid-containingceramic part;

[0034]FIG. 4 illustrates an exemplary processing reactor in which adiamondoid-containing film may be synthesized using chemical vapordeposition (CVD) techniques, including the use of the diamondoidstriamantane and higher to nucleate a film grown “conventionally” byplasma CVD techniques;

[0035]FIG. 5A illustrates an exemplary diamondoid-containing film thatmay be fabricated by self-assembly techniques;

[0036]FIG. 5B illustrates a chelate-derived linker comprising adecamantane; the linker which may comprise a linear bridging unit forconnecting molecular electronic and electro-optical devices;

[0037]FIG. 5C illustrates a chelate-derived linker comprising anonamantane; the linker may comprise a two-dimensional bridging unit forconnecting molecular electronic and electro-optical devices;

[0038] FIGS. 6A-C illustrate an exemplary heat transfer application, inwhich a thermally-conducting film and/or fiber facilitates heatdissipation from an integrated circuit (IC) to a conventional heat sink;

[0039] FIGS. 7A-B illustrate an exemplary heat transfer application inwhich a diamondoid-containing material is used as a thermally-conductivefilm, in this case adhering-two objects together, the two objects beingmaintained at two different temperatures in a situation where rapid heatflow between the two objects is desired;

[0040]FIG. 8 illustrates an exemplary heat transfer application, inwhich a diamondoid-containing material is used in a thermoelectriccooler (or Peltier-based device);

[0041]FIG. 9 is a schematic a cross-section of a typical integratedcircuit, in this case a complementary metal oxide semiconductor (CMOS)device, illustrating where diamondoid-containing materials may be usedas low-k dielectric layers in back-end multilevel interconnectionprocessing, and as passivation layers protecting the top surface of theIC; and

[0042]FIG. 10 illustrates schematically a cross-section of a fieldemission cathode, illustrating where a diamondoid ordiamondoid-containing material may be used as a cold cathode filament,taking advantage of the negative electron affinity of a diamondoidsurface.

DETAILED DESCRIPTION OF THE INVENTION

[0043] According to embodiments of the present invention, diamondoidsare isolated from an appropriate feedstock, and then fabricated into amaterial that is specific for a particular microelectronics application.In the following discussion diamondoids will first be defined, followedby a description of how they may be recovered from petroleum feedstocks.After recovery diamondoids may be processed into polymers, sinteredceramics, and other forms of diamondoid-containing materials, dependingon the application in which they are to be used.

[0044] Definition of Diamondoids

[0045] The term “diamondoids” refers to substituted and unsubstitutedcaged compounds of the adamantane series including adamantane,diamantane, triamantane, tetramantane, pentamantane, hexamantane,heptamantane, octamantane, nonamantane, decamantane, undecamantane, andthe like, including all isomers and stereoisomers thereof. The compoundshave a “diamondoid” topology, which means their carbon atom arrangementis superimposable on a fragment of an FCC diamond lattice. Substituteddiamondoids comprise from 1 to 10 and preferably 1 to 4independently-selected alkyl substituents. Diamondoids include “lowerdiamondoids” and “higher diamondoids,” as these terms are definedherein, as well as mixtures of any combination of lower and higherdiamondoids.

[0046] The term “lower diamondoids refers to adamantane, diamantane andtriamantane and any and/or all unsubstituted and substituted derivativesof adamantane, diamantane and triamantane. These lower diamondoidcomponents show no isomers or chirality and are readily synthesized,distinguishing them from “higher diamondoids.”

[0047] The term “higher diamondoids” refers to any and/or allsubstituted and unsubstituted tetramantane components; to any and/or allsubstituted and unsubstituted pentamantane components; to any and/or allsubstituted and unsubstituted hexamantane components; to any and/or allsubstituted and unsubstituted heptamantane components; to any and/or allsubstituted and unsubstituted octamantane components; to any and/or allsubstituted and unsubstituted nonamantane components; to any and/or allsubstituted and unsubstituted decamantane components; to any and/or allsubstituted and unsubstituted undecamantane components; as well asmixtures of the above and isomers and stereoisomers of tetramantane,pentamantane, hexamantane, heptamantane, octamantane, nonamantane,decamantane, and undecamantane.

[0048] Adamantane chemistry has been reviewed by Fort, Jr. et al. in“Adamantane: Consequences of the Diamondoid Structure,” Chem. Rev. vol.64, pp. 277-300 (1964). Adamantane is the smallest member of thediamondoid series and may be thought of as a single cage crystallinesubunit. Diamantane contains two subunits, triamantane three,tetramantane four, and so on. While there is only one isomeric form ofadamantane, diamantane, and triamantane, there are four differentisomers of tetramantane (two of which represent an enantiomeric pair),i.e., four different possible ways of arranging the four adamantanesubunits. The number of possible isomers increases non-linearly witheach higher member of the diamondoid series, pentamantane, hexamantane,heptamantane, octamantane, nonamantane, decamantane, etc.

[0049] Adamantane, which is commercially available, has been studiedextensively. The studies have been directed toward a number of areas,such as thermodynamic stability, functionalization, and the propertiesof adamantane-containing materials. For instance, the following patentsdiscuss materials comprising adamantane subunits: U.S. Pat. No.3,457,318 teaches the preparation of polymers from alkenyl adamantanes;U.S. Pat. No. 3,832,332 teaches a polyamide polymer forms fromalkyladamantane diamine; U.S. Pat. No. 5,017,734 discusses the formationof thermally stable resins from adamantane derivatives; and U.S. Pat.No. 6,235,851 reports the synthesis and polymerization of a variety ofadamantane derivatives.

[0050] In contrast, the higher diamondoids, have received comparativelylittle attention in the scientific literature. McKervay et al. havereported the synthesis of anti-tetramantane in low yields using alaborious, multistep process in “Synthetic Approaches to LargeDiamondoid Hydrocarbons,” Tetrahedron, vol. 36, pp. 971-992 (1980). Tothe inventor's knowledge, this is the only higher diamondoid that hasbeen synthesized to date. Lin et al. have suggested the existence of,but did not isolate, tetramantane, pentamantane, and hexamantane in deeppetroleum reservoirs in light of mass spectroscopic studies, reported in“Natural Occurrence of Tetramantane (C₂₂H₂₈), Pentamantane (C₂₆H₃₂) andHexamantane (C₃₀H₃₆) in a Deep Petroleum Reservoir,” Fuel, vol. 74(10),pp. 1512-1521 (1995). The possible presence of tetramantane andpentamantane in pot material after a distillation of adiamondoid-containing feedstock has been discussed by Chen et al. inU.S. Pat. No. 5,414,189.

[0051] The four tetramantane structures are iso-tetramantane [1(2)3],anti-tetramantane [121] and two enantiomers of skew-tetramantane [123],with the bracketed nomenclature for these diamondoids in accordance witha convention established by Balaban et al. in “Systematic Classificationand Nomenclature of Diamond Hydrocarbons-I,” Tetrahedron vol. 34, pp.3599-3606 (1978). All four tetramantanes have the formula C₂₂H₂₈(molecular weight 292). There are ten possible pentamantanes, ninehaving the molecular formula C₂₆H₃₂ (molecular weight 344) and amongthese nine, there are three pairs of enantiomers represented generallyby [12(1)3], [1234], [1213] with the nine enantiomeric pentamantanesrepresented by [12(3)4], [1(2,3)4], [1212]. There also exists apentamantane [1231] represented by the molecular formula C₂₅H₃₀(molecular weight 330).

[0052] Hexamantanes exist in thirty-nine possible structures with twentyeight having the molecular formula C₃₀H₃₆ (molecular weight 396) and ofthese, six are symmetrical; ten hexamantanes have the molecular formulaC₂₉H₃₄ (molecular weight 382) and the remaining hexamantane [12312] hasthe molecular formula C₂₆H₃₀ (molecular weight 342).

[0053] Heptamantanes are postulated to exist in 160 possible structureswith 85 having the molecular formula C₃₄H₄₀ (molecular weight 448) andof these, seven are achiral, having no enantiomers. Of the remainingheptamantanes 67 have the molecular formula C₃₃H₃₈ (molecular weight434), six have the molecular formula C₃₂H₃₆ (molecular weight 420) andthe remaining two have the molecular formula C₃₀H₃₄ (molecular weight394).

[0054] Octamantanes possess eight of the adamantane subunits and existwith five different molecular weights. Among the octamantanes, 18 havethe molecular formula C₃₄H₃₈ (molecular weight 446). Octamantanes alsohave the molecular formula C₃₈H₄₄ (molecular weight 500); C₃₇H₄₂(molecular weight 486); C₃₆H₄O (molecular weight 472), and C₃₃H₃₆(molecular weight 432).

[0055] Nonamantanes exist within six families of different molecularweights having the following molecular formulas: C₄₂H₄₈ (molecularweight 552), C₄₁H₄₆ (molecular weight 538), C₄₀H₄₄ (molecular weight524, C₃₈H₄₂ (molecular weight 498), C₃₇H₄₀ (molecular weight 484) andC₃₄H₃₆ (molecular weight 444).

[0056] Decamantane exists within families of seven different molecularweights. Among the decamantanes, there is a single decamantane havingthe molecular formula C₃₅H₃₆ (molecular weight 456) which isstructurally compact in relation to the other decamantanes. The otherdecamantane families have the molecular formulas: C₄₆H₅₂ (molecularweight 604); C₄₅H₅₀ (molecular weight 590); C₄₄H₄₈ (molecular weight576); C₄₂H₄₆ (molecular weight 550); C₄₁H₄₄ (molecular weight 536); andC₃₈H₄₀ (molecular weight 496).

[0057] Undecamantane exists within families of eight different molecularweights. Among the undecamantanes there are two undecamantanes havingthe molecular formula C₃₉H₄₀ (molecular weight 508) which arestructurally compact in relation to the other undecamantanes. The otherundecamantane families have the molecular formulas C₄₁H₄₂ (molecularweight 534); C₄₂H₄₄ (molecular weight 548); C₄₅H₄₈ (molecular weight588); C₄₆H₅₀ (molecular weight 602); C₄₈H₅₂ (molecular weight 628);C₄₉H₅₄ (molecular weight 642); and C₅₀H₅₆ (molecular weight 656).

[0058]FIG. 1 shows a process flow illustrated in schematic form, whereindiamondoids may be extracted from petroleum feedstocks 10 in a step 11processed into a useful form in a step 12, and then incorporated into aspecific microelectronics application shown generally at referencenumeral 13.

[0059] Isolation of Diamondoids from Petroleum Feedstocks

[0060] Feedstocks that contain recoverable amounts of higher diamondoidsinclude, for example, natural gas condensates and refinery streamsresulting from cracking, distillation, coking processes, and the like.Particularly preferred feedstocks originate from the Norphlet Formationin the Gulf of Mexico and the LeDuc Formation in Canada.

[0061] These feedstocks contain large proportions of lower diamondoids(often as much as about two thirds) and lower but significant amounts ofhigher diamondoids (often as much as about 0.3 to 0.5 percent byweight). The processing of such feedstocks to remove non-diamondoids andto separate higher and lower diamondoids (if desired) can be carried outusing, by way of example only, size separation techniques such asmembranes, molecular sieves, etc., evaporation and thermal separatorseither under normal or reduced pressures, extractors, electrostaticseparators, crystallization, chromatography, well head separators, andthe like.

[0062] A preferred separation method typically includes distillation ofthe feedstock. This can remove low-boiling, non-diamondoid components.It can also remove or separate out lower and higher diamondoidcomponents having a boiling point less than that of the higherdiamondoid(s) selected for isolation. In either instance, the lower cutswill be enriched in lower diamondoids and low boiling pointnon-diamondoid materials. Distillation can be operated to provideseveral cuts in the temperature range of interest to provide the initialisolation of the identified higher diamondoid. The cuts, which areenriched in higher diamondoids or the diamondoid of interest, areretained and may require further purification. Other methods for theremoval of contaminants and further purification of an enricheddiamondoid fraction can additionally include the following nonlimitingexamples: size separation techniques, evaporation either under normal orreduced pressure, sublimation, crystallization, chromatography, wellhead separators, flash distillation, fixed and fluid bed reactors,reduced pressure, and the like.

[0063] The removal of non-diamondoids may also include a pyrolysis stepeither prior or subsequent to distillation. Pyrolysis is an effectivemethod to remove hydrocarbonaceous, non-diamondoid components from thefeedstock. It is effected by heating the feedstock under vacuumconditions, or in an inert atmosphere, to a temperature of at leastabout 390° C., and most preferably to a temperature in the range ofabout 410 to 450° C. Pyrolysis is continued for a sufficient length oftime, and at a sufficiently high temperature, to thermally degrade atleast about 10 percent by weight of the non-diamondoid components thatwere in the feed material prior to pyrolysis. More preferably at leastabout 50 percent by weight, and even more preferably at least 90 percentby weight of the non-diamondoids are thermally degraded.

[0064] While pyrolysis is preferred in one embodiment, it is not alwaysnecessary to facilitate the recovery, isolation or purification ofdiamondoids. Other separation methods may allow for the concentration ofdiamondoids to be sufficiently high given certain feedstocks such thatdirect purification methods such as chromatography including preparativegas chromatography and high performance liquid chromatography,crystallization, fractional sublimation may be used to isolatediamondoids.

[0065] Even after distillation or pyrolysis/distillation, furtherpurification of the material may be desired to provide selecteddiamondoids for use in the compositions employed in this invention. Suchpurification techniques include chromatography, crystallization, thermaldiffusion techniques, zone refining, progressive recrystallization, sizeseparation, and the like. For instance, in one process, the recoveredfeedstock is subjected to the following additional procedures: 1)gravity column chromatography using silver nitrate impregnated silicagel; 2) two-column preparative capillary gas chromatography to isolatediamondoids; 3) crystallization to provide crystals of the highlyconcentrated diamondoids.

[0066] An alternative process is to use single or multiple column liquidchromatography, including high performance liquid chromatography, toisolate the diamondoids of interest. As above, multiple columns withdifferent selectivities may be used. Further processing using thesemethods allow for more refined separations which can lead to asubstantially pure component.

[0067] Detailed methods for processing feedstocks to obtain higherdiamondoid compositions are set forth in U.S. Provisional PatentApplication No. 60/262,842 filed Jan. 19, 2001; U.S. Provisional PatentApplication No. 60/300,148 filed Jun. 21, 2001; and U.S. ProvisionalPatent Application No. 60/307,063 filed Jul. 20, 2001. Theseapplications are herein incorporated by reference in their entirety.

[0068] Materials Preparation

[0069] The term “materials preparation” as used herein refers toprocesses that take the diamondoids of interest as they are isolatedfrom feedstocks, and fabricate them into diamondoid-containing materialsfor use in microelectronic applications. These processes may include thederivatization of diamondoids, the polymerization of derivatized andunderivatized diamondoids, the sintering of diamondoid components intoceramics and ceramic composites, the use of diamondoids as a carbonprecursor in conventional CVD techniques, including the use of thediamondoids triamantane and higher to nucleate a diamond film usingconventional CVD techniques (such as thermal CVD, laser CVD,plasma-enhanced or plasma-assisted CVD, electron beam CVD, and thelike), and self-assembly techniques involving diamondoids.

[0070] Methods of forming diamondoid derivatives, and techniques forpolymerizing derivatized diamondoids, are discussed in U.S. patentapplication Ser. No. 60/334,939, entitled “Polymerizable HigherDiamondoid Derivatives,” by Shenggao Liu, Jeremy E. Dahl, and Robert M.Carlson, filed Dec. 4, 2001, and incorporated herein by reference in itsentirety.

[0071] To fabricate a polymeric film containing diamondoid constituents,either as part of the main polymeric chain, or as side groups orbranches off of the main chain, one first synthesizes a derivatizeddiamondoid molecule, that is to say, a diamondoid having at least onefunctional group substituting one of the original hydrogens. Asdiscussed in that application, there are two major reaction sequencesthat may be used to derivatize higher diamondoids: nucleophilic(S_(N)1-type) and electrophilic (S_(E)2-type) substitution reactions.

[0072] S_(N)1-type reactions involve the generation of higher diamondoidcarbocations, which subsequently react with various nucleophiles. Sincetertiary (bridgehead) carbons of higher diamondoids are considerablymore reactive then secondary carbons under S_(N)1 reaction conditions,substitution at a tertiary carbon is favored.

[0073] S_(E)2-type reactions involve an electrophilic substitution of aC—H bond via a five-coordinate carbocation intermediate. Of the twomajor reaction pathways that may be used for the functionalization ofhigher diamondoids, the S_(N)1-type may be more widely utilized forgenerating a variety of higher diamondoid derivatives. Mono andmulti-brominated higher diamondoids are some of the most versatileintermediates for functionalizing higher diamondoids. Theseintermediates are used in, for example, the Koch-Haaf, Ritter, andFriedel-Crafts alkylation and arylation reactions. Although directbromination of higher diamondoids is favored at bridgehead (tertiary)carbons, brominated derivatives may be substituted at secondary carbonsas well. For the latter case, when synthesis is generally desired atsecondary carbons, a free radical scheme is often employed.

[0074] Although the reaction pathways described above may be preferredin some embodiments of the present invention, many other reactionpathways may certainly be used as well to functionalize a higherdiamondoid. These reaction sequences may be used to produce derivatizeddiamondoids having a variety of functional groups, such that thederivatives may include diamondoids that are halogenated with elementsother than bromine, such as fluorine, alkylated diamondoids, nitrateddiamondoids, hydroxylated diamondoids, carboxylated diamondoids,ethenylated diamondoids, and aminated diamondoids. See Table 2 of theco-pending application “Polymerizable Higher Diamondoid Derivatives” fora listing of exemplary substituents that may be attached to higherdiamondoids.

[0075] Diamondoids, as well as diamondoid derivatives havingsubstituents capable of entering into polymerizable reactions, may besubjected to suitable reaction conditions such that polymers areproduced. The polymers may be homopolymers or heteropolymers, and thepolymerizable diamondoid derivatives may be co-polymerized withnondiamondoid-containing monomers. Polymerization is typically carriedout using one of the following methods: free radical polymerization,cationic, or anionic polymerization, and polycondensation. Proceduresfor inducing free radical, cationic, anionic polymerizations, andpolycondensation reactions are well known in the art.

[0076] Free radical polymerization may occur spontaneously upon theabsorption of an adequate amount of heat, ultraviolet light, orhigh-energy radiation. Typically, however, this polymerization processis enhanced by small amounts of a free radical initiator, such asperoxides, azo compounds, Lewis acids, and organometallic reagents. Freeradical polymerization may use either non-derivatized or derivatizedhigher diamondoid monomers. As a result of the polymerization reaction acovalent bond is formed between diamondoid monomers such that thediamondoid becomes part of the main chain of the polymer. In anotherembodiment, the functional groups comprising substituents on adiamondoid may polymerize such that the diamondoids end up beingattached to the main chain as side groups. Diamondoid having more thanone functional group are capable of cross-linking polymeric chainstogether.

[0077] For cationic polymerization, a cationic catalyst may be used topromote the reaction. Suitable catalysts are Lewis acid catalysts, suchas boron trifluoride and aluminum trichloride. These polymerizationreactions are usually conducted in solution at low-temperature.

[0078] In anionic polymerizations, the derivatized diamondoid monomersare typically subjected to a strong nucleophilic agent. Suchnucleophiles include, but are not limited to, Grignard reagents andother organometallic compounds. Anionic polymerizations are oftenfacilitated by the removal of water and oxygen from the reaction medium.

[0079] Polycondensation reactions occur when the functional group of onediamondoid couples with the functional group of another; for example, anamine group of one diamondoid reacting with a carboxylic acid group ofanother, forming an amide linkage. In other words, one diamondoid maycondense with another when the functional group of the first is asuitable nucleophile such as an alcohol, amine, or thiol group, and thefunctional group of the second is a suitable electrophile such as acarboxylic acid or epoxide group. Examples of higherdiamondoid-containing polymers that may be formed via polycondensationreactions include polyesters, polyamides, and polyethers.

[0080] Exemplary diamondoid-containing polymeric films are illustratedschematically in FIGS. 2A-2C. Referring to FIG. 2A, adiamondoid-containing polymer is shown generally at 200, where thepolymer comprises diamondoid monomers 201, 202, 203 linked throughcarbon-to-carbon covalent bonds 204. The diamondoid monomers 201, 202,203 may comprise any member of the higher diamondoid series tetramantanethrough undecamantane. The covalent linkage 204 comprises a bond betweentwo carbon atoms where each of carbon atoms of the bond are members ofthe two adjacent diamondoids. Stated another way, two diamondoids in thepolymeric chain are directly linked such that there are no interveningcarbon atoms that are not part of a diamondoid nucleus (or part of anadamantane subunit).

[0081] Alternatively, two adjacent diamondoids may be covalently linkedthrough carbon atoms that are not members (part of the carbon nucleus)of either of the two diamondoids. Such a covalent linkage is shownschematically in FIG. 2A at reference numeral 205. As discussed above,adjacent diamondoids may be covalently connected through, for example,an ester linkages 206, an amide linkages 207, and an ether linkage is208.

[0082] In an alternative embodiment, a diamondoid-containing polymershown generally at 220 in FIG. 2B comprises a copolymer formed from themonomers ethylene and a higher diamondoid having at least one ethylenesubstituent. The diamondoid monomer shown at 221 contains onesubstituent ethylene group. The diamondoid monomer shown at 222 containstwo ethylene substituents, and could have more than two substituents.Either or both of these diamondoids may be copolymerized with ethylene223 itself, as a third monomer participating in the reaction, to formthe co-polymer 220 or subunits thereof. Because the diamondoid monomer222 has two substituent polymerizable moieties attached to it, thisparticular monomer is capable of cross-linking chains 224 and chain 225together. Such a cross-linking reaction is capable of producing polymershaving properties other than those of the polymer depicted in FIG. 2A,since for the FIG. 2A polymer the diamondoid nuclei are positionedwithin the main chain. A consequence of the structures formed in FIGS.2A and 2B is that it is possible to incorporate metallic elements,particles, and inclusions (illustrated as M1 to M3) by inserting theminto the interstities of folded and cross-linked polymeric chains.Diamondoid-containing materials may be doped in such a manner withalkali metals, alkali earth metals, halogens, rare earth elements, B,Al, Ga, In, TI, V, Nb, and Ta to improve thermal conductivity ifdesired. The relative ratios of the monofunctional diamondoid monomer,the difunctional diamondoid monomer, and the ethylene monomer in theexemplary polymer of FIG. 2B may of course be adjusted to produce thedesired properties with regard to stiffness, compactness, and ease ofprocessing.

[0083] The exemplary polyimide-diamondoid polymer shown generally at 230in FIG. 2C contains segments of polyimide chains derived fromrepresentative groups selected to illustrate certain relationshipsbetween structure and properties, in particular, how the properties ofthe exemplary polymer relate to the processing it has undergone. Thedianhydride PMDA (pyromellitic dianhydride) shown at 231 and the diaminediaminofluorenone 232 are introduced into the chain for rigidity. Thedianhydride BTDA (benzophenonetetracarboxylic dianhydride) shown at 233provides the capability of further reaction at the carboxyl site,possibly for crosslinking purposes, and/or for the potential inclusionof metallic moieties into the material. The dianhydride oxydiphthalicdianhydride (ODPA) shown at 234, and the diamines oxydianiline (ODA) at235 and bisaminophenoxybenzene at 236 may be introduced for chainflexibility and ease of processing of the material. Additionally,fluorinated dianhydrides such as 6FDA (not shown) may be introduced tolower the overall dielectric constant of the material.

[0084] The diamondoid components of the exemplary polymer illustratedschematically in FIG. 2C comprise a pentamantane diamondoid at 266,which is positioned in the main chain of the polymer, and an octamantanediamondoid at 237, which comprises a side group of thediamondoid-polyimide polymer at a position of a diamine (in thisexemplary case, diaminobenzophenone) component. A diamondoid component238 may be used as a cross-linking agent to connect two adjacent chains,through covalent linkages, or diamondoid component 238 may be passivelypresent as an unfunctionalized “space filler” wherein it serves toseparate main polymeric chains simply by steric hindrance. Folding ofthe main polymeric chains, particularly when diamondoid “fillers” 238are present, may create voids 239, which may serve to reduce the overalldielectric constant of the material, since the dielectric constant ofair (if it is the gas within the void), is one.

[0085] The diamond nanocrystallites (higher diamondoids) that may beincorporated into a diamondoid-containing material in general, and intopolymeric materials in particular, have a variety of well-definedmolecular structures, and thus they may be attached to each other,attached to a main polymer chain, used as cross-lining agents, etc., ina great variety of ways. The six hexamantanes illustrated in FIG. 2D areexamples of a higher diamondoid having a highly symmetrical shape, andthe 12 chiral hexamantanes illustrated in FIG. 2E are examples ofenantiomeric pairs.

[0086] The molecular sites and the geometries of the attachments of ahigher diamondoid to another diamondoid, and to a polymer chain, willalso affect the properties of resulting materials. For example, theinterconnection of higher diamondoid units through tertiary“bridge-head” carbons, as illustrated in FIG. 2F, will result instronger, more rigid materials than those which result frominterconnection through secondary carbons, as in FIG. 2G. Furthermore,attachment through tertiary carbons that are themselves bonded to thehighest number of quaternary carbons in a higher diamondoid(nanocrystallite) will provide the strongest, most rigid materials, asin FIG. 2H.

[0087] There are other properties of higher diamondoids that may beexploited to design new materials with desirable properties. Higherdiamondoids display classical diamond crystal faces such as the (111),(110), and (100) planes, as shown in FIGS. 2I, 2J, and 2K for thediamondoid [1(2,3)4] pentamantane illustrated in FIG. 2N. These higherdiamondoids may be oriented in materials such as polymers so that theresulting diamond nanocrystallites may have co-planer diamond faces. Thediamondoids with chiral sturcture, may be used to fabricate theexemplary chiral polymers illustrated in FIGS. 2L, 2M. These kinds ofchiral polymers have potential uses in photonics, and for theintegration of photonic and electronic devices.

[0088] The diamondoid-containing polymers discussed above may be appliedto a substrate undergoing microelectronic processing by any of methodsknown in the art, such as spin coating, molding, extrusion, and vaporphase deposition.

[0089] The weight of diamondoids and substituted diamondoids as afunction of the total weight of the polymer (where the weight of thediamondoid functional groups are included in the diamondoid portion) mayin one embodiment range from about 1 to 100 percent by weight. Inanother embodiment, the content of diamondoids and substituteddiamondoids is about 10 to 100 percent by weight. In another embodiment,the proportion of diamondoids and substituted diamondoids in the polymeris about 25 to 100 percent by weight of the total weight of the polymer.

[0090] Another technique that may be used to form isolated diamondoidsinto useful and application-specific shapes is sintering, usingprocesses that typically are used in the ceramics industry. Ceramicshave been defined by M. Barsoum in Fundamentals of Ceramics (McGrawHill, New York, 1997), pp. 2-3. In general, ceramics may be defined assolids formed by heating (often under pressure) mixtures of metals,nonmetallic elements such as nitrogen, oxygen, hydrogen, fluorine, andchlorine, and “nonmetallic elemental solids” including carbon, boron,phosphorus, and sulfur. Ceramics have varying degrees of ionic andcovalent bonding. Many of the hardest, most refractory, and toughestceramics are structures in which covalent bonding predominates. Examplesof covalent ceramics are boron nitride (BN), silicon carbide (SiC),boron carbide (B₄C), silicon nitride (Si₃N₄). Although un-derivatizeddiamondoids will most likely form van der Waals solids with a certaincohesive energy exerted between adjacent surface carbons and theirattached hydrogens, diamondoids may be derivatized as discussed abovesuch that they possess functionality on their surfaces capable ofinteracting both ionically, and covalently, with other ceramicmaterials. Such solids may be thought of as behaving in general like aceramic, but having small, diamond-like particulate inclusions.

[0091] A process flow for generating the diamondoid-containing ceramicand/or ceramic composite is shown generally in FIG. 3A. Shown atreference numeral 301 is the isolation of diamondoids from feedstocks.The isolated diamondoids may then be derivatized with the desiredfunctional groups as discussed above, as shown at 302. However, in someembodiments, it may not be necessary to derivatize the diamondoids. At303, the diamondoids (which may or may not be derivatized) may be mixedwith a nondiamondoid powder, the latter which may comprise any otherceramic materials known in the art. An exemplary list of such ceramicsis given by Chiang et al. in “Physical Ceramics,” Table 1.3 (Wiley, NewYork, 1997), incorporated herein in entirety by reference. It will beapparent to one skilled in the art that a substituent may be attached tothe diamondoid, the substituent belonging to Group IA or Group IIA ofthe periodic table such that the the substituent will be an electrondonor. Such elements are useful if a high degree of ionic character isdesired. Examples of such elements include Li, Be, Na, Mg, K, Ca, andSr. Alternatively, powders containing metal particles 305 from GroupsIIIB to 11B may be mixed with the diamondoid materials including alloysof such metals. Noble metals such as Au, Ag, Pa, Pt and their alloys maybe desirable since these materials are less susceptible to oxidation.Non-noble metals such as Cu, Ni, Fe, Co, Mo, W, V, Zn, and Ti, and theiralloys, may also be used. Low melting point metals such as Sn, Al, Sb,In, Bi, Pb, and their alloys, or conventional low melting point soldersmay be mixed with the diamondoids, as well as semiconducting materialssuch as Si and Ge. The diamondoids may also be mixed with organometalliccompounds to convey a desired degree of electrical conductivity to theresulting ceramic, and these organometallic compounds may reactcovalently with functional groups on the diamondoids.

[0092] The mixing of the functionalized and/or non-functionalizeddiamondoids with ceramic and/or metal powders is performed by way ofexample as a dry process, such as stirring or ball milling, or as a wetprocess forming a powder mixed slurry incorporating a liquid capable ofbeing evaporated (such as alcohol, acetone, and water), optionally withthe addition of a binder to improve the adhesion of the constituentparticles to one another.

[0093] The mixture may then be sintered at elevated pressure andtemperature, according to processes well known in the art, to yield aceramic solid and/or ceramic composite. It may be preferable to machinethe sintered product into a specific shape at 308, or the sinteringproduct at 307 may be formed in a mold such that the sintered producthas the desired shape. Prior to sintering, the mixture 306 may bepressed into a green shape 309 although this step is optional. Thepressing step 309 is advantageous in some instances in that it mayeliminate the trapping of gases, although it will be noted by oneskilled in the art that in some applications a porosity is desired. Thepressing step 309 may also allow soft metals, such as solders, ifpresent, to flow within the system. In some embodiments, the pressingstep 309 may be performed in conjunction with a vacuum applied to any orall of the mixture to facilitate shaping of the solid, or to removeundesired gaseous byproducts.

[0094] One such exemplary sintered diamondoid-containing ceramic and/orceramic composite is illustrated schematically in FIG. 3B. The sintereddiamondoid-containing ceramic is shown generally at 320, wherediamondoid particles 321, 322, and 323 are shown. The diamondoidparticle at 321 may be derivatized such that it is bound in the ceramicmaterial by chemical bonds, or the diamondoids may be underivatized andbound in the material substantially by mechanical forces. In analternative embodiment, the diamondoid particles and/or diamondoidaggregates at 322 and 323 may contain functional groups 324 and 325,respectively, to facilitate adhesion of the diamondoid particles toceramic particles 326. Alternatively, a binder 327 may be present tofacilitate adhesion of diamondoid particles 322 and 323 to ceramicparticles 326, in some cases by forming covalent bonds throughfunctional groups 324 and 325. Large metallic inclusions 328 may bepresent to facilitate electrical conduction.

[0095] The ceramic shown generally at 320 may be processed into specificshapes and forms, having for example protrusions 330 for nesting andpositioning the ceramic in place, or regions 331 that may have specificactive functions. The shaping step 308 (see again FIG. 3A) may beaccomplished by any of the techniques known in the art, such as forging,machining, grinding, or stamping.

[0096] The weight of diamondoids and substituted diamondoids as afunction of the total weight of the ceramic (where the weight of thediamondoid functional groups are included in the diamondoid portion) mayin one embodiment range from about 1 to 99.9 percent by weight. Inanother embodiment, the content of diamondoids and substituteddiamondoids is about 10 to 99 percent by weight. In another embodiment,the proportion of diamondoids and substituted diamondoids in the ceramicis about 25 to 95 percent by weight of the total weight of the ceramic.

[0097] Thus far, the present description has focused on polymerizationand ceramic sintering as techniques for forming diamondoids intoapplication specific forms. Two additional techniques, chemical vapordeposition (CVD) and self-assembly, will be discussed next. Forinstance, conventional methods of synthesizing diamond by plamsaenhanced chemical vapor deposition (PECVD) techniques are well known inthe art, and date back to around the early 1980's. Although it is notnecessary to discuss the specifics of these methods as they relate tothe present invention, one point in particular that should be made sinceit is relevant to the role hydrogen plays in the synthesis of diamond by“conventional” plasma-CVD techniques.

[0098] In one method of synthesizing diamond films discussed by A.Erdemir et al. in “Tribology of Diamond, Diamond-Like Carbon, andRelated Films,” in Modern Tribology Handbook, Vol. Two, B. Bhushan, Ed.(CRC Press, Boca Raton, 2001) pp. 871-908, a modified microwave CVDreactor is used to deposit a nanocrystalline diamond film using a C₆₀fullerene, or methane, gas carbon precursor. This method differs fromconventional CVD techniques in that the deposition was conducted in theabsence of hydrogen, with argon used instead. Methane/argon gas mixturesare being increasingly used when nanocrystalline diamond films aredesired, as discussed above. To introduce the C₆₀ fullerene precursorinto the reactor, a device called a “quartz transpirator” is attached tothe reactor, wherein this device essentially heats a fullerene-rich sootto temperatures between about 550 and 600° C. to sublime the C₆₀fullerene into the gas phase.

[0099] It is contemplated that a similar device may be used to sublimediamondoids into the gas phase such that they to may be introduced to aCVD reactor. An exemplary reactor is shown in generally at 400 in FIG.4. A reactor 400 comprises reactor walls 401 enclosing a process space402. A gas inlet tube 403 is used to introduce process gas into theprocess space 402, the process gas comprising methane, hydrogen, andoptionally an inert gas such as argon. A diamondoid subliming orvolatilizing device 404, similar to the quartz transpirator discussedabove, may be used to volatilize and inject a diamondoid containing gasinto the reactor 400. The volatilizer 404 may include a means forintroducing a carrier gas such as hydrogen, nitrogen, argon, or an inertgas such as a noble gas other than argon, and it may contain othercarbon precursor gases such as methane, ethane, or ethylene.

[0100] Consistent with conventional CVD reactors, the reactor 400 mayhave exhaust outlets 405 for removing process gases from the processspace 402; an energy source for coupling energy into process space 402(and striking a plasma from) process gases contained within processspace 402; a filament 407 for converting molecular hydrogen tomonoatomic hydrogen; a susceptor 408 onto which a diamondoid containingfilm 409 is grown; a means 410 for rotating the susceptor 408 forenhancing the sp³-hybridized uniformity of the diamondoid-containingfilm 409; and a control system 411 for regulating and controlling theflow of gases through inlet 403, the amount of power coupled from source406 into the processing space 402; and the amount of diamondoidsinjected into the processing space 402 the amount of process gasesexhausted through exhaust ports 405; the atomization of hydrogen fromfilament 407; and the means 410 for rotating the susceptor 408. In anexemplary embodiment, the plasma energy source 406 comprises aninduction coil such that power is coupled into process gases withinprocessing space 402 to create a plasma 412.

[0101] A diamondoid precursor (which may be a triamantane or higherdiamondoid) may be injected into reactor 400 according to embodiments ofthe present invention through the volatilizer 404, which serves tovolatilize the diamondoids. A carrier gas such as methane or argon maybe used to facilitate transfer of the diamondoids entrained in thecarrier gas into the process space 402. The injection of suchdiamondoids may facilitate growth of a CVD grown diamond film 409 byallowing carbon atoms to be deposited at a rate of about 10 to 100 ormore at a time, unlike conventional plasma CVD diamond techniques inwhich carbons are added to the growing film one atom at a time. Growthrates may be increased by at least two to three times and in someembodiments, growth rates may be increased by at least an order ofmagnitude.

[0102] It may be necessary, in some embodiments, for the injectedmethane and/or hydrogen gases to “fill in” diamond material betweendiamondoids, and/or “repair” regions of material that are “trapped”between the aggregates of diamondoids on the surface of the growing film409. Hydrogen participates in the synthesis of diamond by PECVDtechniques by stabilizing the sp³ bond character of the growing diamondsurface. As discussed in the reference cited above, A. Erdemir et al.teach that hydrogen also controls the size of the initial nuclei,dissolution of carbon and generation of condensable carbon radicals inthe gas phase, abstraction of hydrogen from hydrocarbons attached to thesurface of the growing diamond film, production of vacant sites where spbonded carbon precursors may be inserted. Hydrogen etches most of thedouble or sp² bonded carbon from the surface of the growing diamondfilm, and thus hinders the formation of graphitic and/or amorphouscarbon. Hydrogen also etches away smaller diamond grains and suppressesnucleation. Consequently, CVD grown diamond films with sufficienthydrogen present leads to diamond coatings having primarily large grainswith highly faceted surfaces. Such films may exhibit the surfaceroughness of about 10 percent of the film thickness. In the presentembodiment, it may not be as necessary to stabilize the surface of thefilm, since carbons on the exterior of a deposited diamondoid arealready sp³ stabilized.

[0103] Diamondoids may act as carbon precursors for a CVD diamond film,meaning that each of the carbons of the diamondoids injected intoprocessing space 402 are added to the diamond film in a substantiallyintact form. In addition to this role, diamondoids 413 injected into thereactor 400 from the volatilizer 404 may serve merely to nucleate a CVDdiamond film grown according to conventional techniques. In such a case,the diamondoids 413 are entrained in a carrier gas, the latter which maycomprise methane, hydrogen, and/or argon, and injected into the reactor400 at the beginning of a deposition process to nucleate a diamond filmthat will grow from methane as a carbon precursor (and not diamondoid)in subsequent steps. In some embodiments, the selection of theparticular isomer of a particular diamondoid may facilitate the growthof a diamond film having a desired crystalline orientation that may havebeen difficult to achieve under conventional circumstances.Alternatively, the introduction of a diamondoid nucleating agent intoreactor 400 from volatilizer 404 may be used to facilitate anultracrystalline morphology into the growing film for the purposesdiscussed above.

[0104] As described by D. M. Gruen in “Nucleation ofultrananocrystalline diamond films” in Properties, Growth, andApplications of Diamond, edited by M. H. Nazaré and A. J. Neves (Inspec,Exeter, 2001), pp. 303-306, in order to obtain ultrananocrystalline filmgrowth having a microstructure consisting of a 3-5 nanometer crystallitesize, the nucleation rate has to increase from a conventional value of10⁴ cm⁻² s⁻¹ to about 10¹⁰ cm⁻² s⁻¹. This 10⁶ order of magnitudeincrease in nucleation rate may be provided by the introduction ofsublimed diamondoids into the reactor 400 at the beginning of a CVDdeposition process.

[0105] It has been pointed out by W. Kulisch in “Deposition ofDiamond-Like Superhard Materials,” Section 4.2, Nucleation of Diamond(Springer, Berlin, 1999), that the nucleation of diamond is complicatedby the fact that one must distinguish between carbide-forming substrates(e.g. Si and Mo) and non-carbide forming substrates (Ni and Pt). In theformer case, the diffusion of carbon into the substrate leads to acarbide layer which acts as a barrier to further carbon diffusion, andan increased carbon concentration on the surface. The barrier is anecessary but not sufficient condition for the rapid formation of nucleion the surface of the substrate. For non-carbide forming substrates, onthe other hand, deposition begins with the formation of a graphitic, andgenerally greater carbon-like layer before any diamond nuclei can beobserved. According to embodiments of the present invention, theinjection of diamondoid containing gases into reactor 400 at thebeginning of a CVD diamond process may render the reaction independentof the nature of the substrate, since the diamondoid particles acting asnuclei are so large and thermodynamically stable that diffusion ofcarbon into the substrate is not practical. In one embodiement, a methodof nucleating the growth of a diamond film involves the injection of atriamantane diamondoid into the CVD reactor at the beginning of adeposition process. In another embodiment, diamondoid film growth isnucleated with a higher diamondoid, where the higher diamondoid maycomprise tetramantane, pentamantane, hexamantane, heptamantane,octamantane, nonamantane, decamantane, and undecamantane, includingcombinations thereof and combinations with triamantane. Of course, thediamondoids mentioned above may be used to nucleate diamond films grownby other types of processes in other types of reactors, and theseembodiments are not limited to chemical vapor deposition.

[0106] The weight of diamondoids and substituted diamondoids, as afunction of the total weight of the CVD film (where the weight of thediamondoid functional groups are included in the diamondoid portion),may in one embodiment range from about 1 to 99.9 percent by weight. Inanother embodiment, the content of diamondoids and substituteddiamondoids is about 10 to 99 percent by weight. In another embodiment,the proportion of diamondoids and substituted diamondoids in the CVDfilm relative to the total weight of the film is about 25 to 95 percentby weight.

[0107] In addition to techniques where diamondoids are used asprecursors for CVD diamond film deposition and nucleation entities,diamondoids may also be incorporated into a film by self-assemblytechniques. Diamondoids and their derivatives can undergo self-assemblyin a variety of ways. For example, diamondoid-thiols may self-assembleon various metal surfaces, as illustrated generally in FIG. 5A, where adiamondoid monolayer 501 has self-assembled on a metal layer 502. Thediamondoids comprising the monolayer 501 may be either lowerdiamondoids, higher diamondoids, or both. If the diamondoids of themonolayer 501 are lower diamondoids, they may be synthesized or isolatedfrom a suitable feedstock. If the diamondoids comprising monolayer 501are higher diamondoids, they may be isolated from a suitable feedstockwhen synthesis is not possible. These selected diamondoids can then bederivatized, in this example, to form a thiol-diamondoid 503. Thethio-diamondoid derivative 503 can then self-assemble, and undergopartial or complete orientation in the process, by bonding to the metalsurface 502. In one embodiment, the metal surface 502 comprises gold ora gold alloy. Alternatively, the diamondoid layer 501 may self-assembleon the metal layer 502 through alkyl sulfide groups, an example of whichmay be represented by the sequence “metal layer502-S—C₁₂H₂₄-diamondoid,” or “metal layer 502-S—R-diamondoid,” where Rrepresents an alkyl group.

[0108] In an alternative embodiment, a diamondoid layer mayself-assemble by hydrogen bonding to either a substrate or to some otherlayer, including another diamondoid-containing layer, or anon-diamondoid containing layer. In the exemplary embodiment illustratedin FIG. 5A, the diamondoid layer 501 has hydrogen-bonded to anon-diamondoid layer 504, such that the diamondoid layer 501 issandwiched between the non-diamondoid layer 504 and the metal layer 502.It will be apparent to those skilled in the art that thehydrogen-bonding of the diamondoid layer 501 to the non-diamondoid layer504 does not require the derivatization of the diamondoid layer 501 ifhydrogens 505 on the diamondoid layer 501 are bonding to hydroxyl groups506 on the non-diamondoid layer 504. Hydrogen bonding could occur,however, between hydroxyl groups on the diamondoids 503 and hydrogens onthe non-diamondoid layer 504, in which case the diamondoids 503 might bederivatized.

[0109] In addition to a chemically based self-assembly, a diamondoid ordiamondoid-containing layer could self-assemble through electrostaticinteractions. This possibility is illustrated at the top of FIG. 5A,where a diamondoid layer 507 has electrostatically self-aligned on thenon-diamondoid layer 504 through electrostatic interactions 508. In thisexample the diamondoid layer 507 has positive charges and the substrateon which it is aligning has negative charges, but of course this couldbe reversed, and there could be a mixture of positive and negativecharges on each layer.

[0110] In addition to the examples cited above, a derivatized diamondoidmay self-assemble on a layer having a plurality of functional groupsthat are complimentary to the derivatizing groups on the diamondoids.Likewise, derivatized diamondoids may polymerize in a self-assemblyingfashion given the complementary nature of functional groups. In otherwords, monomers may be induced to self-assemble into polymers. Theformation of polymers, like the self-assembling chemical reactionsdescribed above, is a method of locking diamondoids into desiredorientations with desired thicknesses. The polymers can be synthesizeddirectly on a desired substrate.

[0111] Formation of molecular crystals is another means of inducingdiamondoids and their derivatives to self-assemble. Once a particulardiamondoid has been isolated and purified (and derivatized if desired),crystals can be grown by slowly evaporating diamondoid solvents such ascyclohexane. By varying conditions such as the temperature, the solventcomposition and the speed of solvent evaporation, the size of theindividual crystals can be controlled. They can range in size fromnanometers to centimeters, depending on the processing conditions. Theresulting self-assembled crystals can orient the diamondoid molecules ina preferred direction or set of directions. Self-assembled crystals maybe grown directly on a desired substrate.

[0112] Higher diamondoid derivatives containing two or more chelationsites can be used to construct nanometer-sized linker units thatself-assemble in the presence of appropriate metal ions to form longchains of alternating metal ion and linker subunits. An example is shownin FIG. 5B, in which [1231241(2)3] decamantane functions as a linearlinker unit. In FIG. 5C, [121(2)₃₂(1)3] nonamantane functions as a2-dimensional linker unit. Linear linkers using only adamantane havebeen described by J. W. Steed et al. in “Supermolecular Chemistry,”(Wiley, New York, 2001), pp. 581-583. Various three-dimensionalself-assembling units are possible given the wide range of higherdiamondoid structures. Additionally, this approach may be used to designlinker units which self-assemble into desired, predetermined arrays.

[0113] The weight of diamondoids and substituted diamondoids that may beincorporated into a self-assembled film, as a function of the totalweight of the film (where the weight of the functional groups areincluded in the diamondoid portion) may in one embodiment range fromabout 1 to 99.99 percent by weight. In another embodiment, the contentof diamondoids and substituted diamondoids is about 10 to 98 percent byweight. In another embodiment, the proportion of diamondoids andsubstituted diamondoids in the ceramic is about 25 to 98 percent byweight of the total weight of the self-assembled film.

[0114] Applications of Diamondoid-Containing Materials toMicroelectronics

[0115] These applications include microelectronics packaging,passivation films for integrated circuit devices (ICs), low-k dielectriclayers in multilevel interconnects, thermally conductive films,including adhesive films, thermoelectric cooling devices, and fieldemission cathodes.

[0116] The process of preparing an integrated circuit (IC) chip for useis called packaging. An overview of IC packaging has been presented byT. Tachikawa in a chapter entitled “Assembly and Packaging,” ULSITechnology (McGraw Hill, New York, 1996), pp. 530-586. The purpose of ICpackaging is to provide electrical connections for the chip, mechanicalenvironmental protection, as well as a conduit for dissipating heat thatevolves as the chip is operated. Integrated circuit devices includememory, logic, and microprocessing devices. Packaging devices includehermetic-ceramic and plastic packages. Each have their own level ofpower dissipation, and pose their own requirements in terms of thethermal path to dissipate heat. Integrated circuit clock speeds andpower densities are increasing, and since package sizes aresimultaneously decreasing, thermal dissipation becomes a long-termpackaging reliability issue. The heat generated by an IC is proportionalto its computing power, which is the product of the number oftransistors in the IC and their clock frequencies. Although thecomputing power of a typical IC has increased significantly in recentyears, design rules such as the operating temperature have notsubstantially changed, placing demands on the methods by whichdissipated heat is removed.

[0117] As discussed by T. Tachikawa, chip interconnection typicallyconsists of two steps. In a first step, the back of the chip ismechanically bonded to an appropriate medium, such as a ceramicsubstrate or the paddle of a metal lead frame. Chip bonding provides,among other things, a thermal path for heat to be dissipated from thechip to the substrate medium. In a second step, the bond pads on thecircuit side of the chip are electrically connected to the package bywire bonding, typically using fine metal wires of gold or aluminum.

[0118] As the amount of heat generated by the integrated circuitincreases, so too does the junction temperature of the componentstransistors in a proportional manner. The failure rate of thesemiconducting device is in general related to the junction temperatureat which the device is operated. It is generally known to provide a heatspreader or heat sink in order to transfer the heat generated by thedevice away from the device and into either the surrounding air or thesubstrate, thus reducing transistor junction temperatures. Heat sinksare typically constructed from materials having high thermalconductivity, such as copper, aluminum, BeO, and diamond, although othermaterial properties are taken into consideration, such as density, andthermal expansion coefficient. Since CVD diamond has a thermalconductivity (up to 2500 W/mK) three to five times greater than that ofcopper (about 391 W/mK) a thermal expansion coefficient similar to thatthe Si and GaAs, and high electrical resistivity, CVD diamond offers anattractive alternative to traditional metallic heat spreading materials,particularly when formed such that they facilitate transfer of heat froman integrated circuit to a conventional metallic heat sink/substrate.

[0119] An exemplary model of a packaged integrated chip is showngenerally at 600 in FIG. 6A to illustrate the processes by which heat isdissipated from an integrated circuit, where a chip 601 is supported bya frame (not shown) within a plastic package 602. Metallic bond wires604A, 604B connect the chip to a lead 605A, 605B, respectively.Dissipated heat is conducted away from the chip by conductive heattransfer along pathways 606 (according to Fourier's equation), byconvection 607 (Newton's cooling law), and by radiation 608 (followingthe Stefan-Boltzmann law).

[0120] In one embodiment of the present invention, a diamondoidcontaining heat transfer film 620 is positioned adjacent to integratedcircuit chip 601 and a heat sink 610 positioned inside the package 625.By providing heat transfer film 620, heat from the integrated circuit601 may diffuse along a pathway 621 in a substantially direct route intothe heat sink material 610, or alternatively, may be conducted alongheat transfer path 622 into the heat sink at 623. This provides anadditional pathway for the removal of heat. By providing heat transferfilm 620, and pathway 622, heat may be dispersed into heat sink 610 atpositions 623 that are laterally displaced from the integrated circuitchip 601, and in this manner, heat removal from integrated circuit 601is facilitated.

[0121] In another embodiment of the present invention, there may not besufficient room within or immediately adjacent to the integrated circuitchip 601 for a heat sink. In FIG. 6C, a larger heat sink 630 ispositioned outside the package 635. In this embodiment, heat pipes orheat conduits 631, 632 may be used to conduct heat away from the chip toa heat sink located remotely from the package. The heat conduits may bein fiber form, and may be inserted into the integrated circuit chipitself at locations 633, 634, or they may communicate with thermal vias(not shown) within the chip. The heat conducting conduits may beflexible fibers, or rigid rods. There may be from about 1 to 100 of theheat conducting fibers or rods.

[0122] The heat transfer film 620 of FIG. 6B, and heat conduits 630 ofFIG. 6C may comprise any of the diamondoid-containing materialsdiscussed above, such as a polymerized diamondoid film, adiamondoid-containing ceramic and/or ceramic composite, a CVD depositeddiamondoid-containing film, a CVD diamond film nucleated by diamondoids,or a diamondoid-containing film deposited by self-assembly techniques.According to one embodiment of the present invention, the heat transferfilm 620 comprises a diamondoid-containing polymer similar to thatdepicted in FIG. 2A, particularly where diamondoid 201 is connected toan adjacent diamondoid 202 through either covalent linkage 204 orcovalent linkage 205. The covalent linkage 204 bonds carbons that aremembers of the diamondoid nucleus itself; alternatively, the covalentlinkage 205 is a bond in which the constituent carbons of the bondcomprise attachments or substituents to the diamondoid nuclei they areconnecting.

[0123] It will be recognized by those skills in the art that sincediamondoids themselves are hydrocarbons, heat transfer within a van derWaals solid will be less efficient than through a polymer having acontinuous network of C—C bonds. The heat transfer film 620 may be verythin, comprising a minor layer of diamondoids such that the heat flow isthrough just the diameter of a single diamondoid. In this manner, asabove, a continuous network of C—C bonds is provided.

[0124] Diamondoids may be used as thermally-conducting films in othermicroelectronics applications, such as an adhesive film, or as anintermediate heat transfer film as part of a thermoelectric coolingdevice. An exemplary application of a thermally conducting adhesive filmis shown generally with device 700 in FIGS. 7A-B. The device 700 in FIG.7A comprises an object 701 at a temperature T₁ adhesively connected toan object 702 at temperature T₂, the connection means comprising athermally-conducting adhesive film 703. In this example, it is desiredto adhere the object 701 to the object 702, with a minimum of resistanceof heat flow between the two bodies. At one time, the temperature T₁ maybe for example greater than the temperature T₂, and in this case, heatwill be allowed to flow flow rapidly from the object 701 to the object702, an interaction 704, with a minimum of thermal resistance.

[0125] As this exemplary device 700 is being operated, the temperaturesof the two bodies may change virtually instantaneously, such that at alater time the temperature of the body 702 is T₄ and the temperature ofthe body 701 is T₃, where T₄ is greater than T₃. As the device is beingoperated into the second configuration of FIG. 7B, it may still bedesirable to adhere to the object 701 to the body 702 with asubstantially minimal resistance to heat flow. In this case, thethermally conducting films 703 allows heat to flow in an reversedirection 705, from the object 702 back to the object 701.

[0126] The thermally-conducting adhesive film 703 may comprise any ofthe material forms discussed above, such as as a polymerized diamondoidfilm, a diamondoid-containing ceramic and/or ceramic composite, a CVDdeposited diamondoid-containing film, a CVD diamond film nucleated bydiamondoids, or a diamondoid-containing film deposited by self-assemblytechniques. In a preferred embodiment, however, the thermally-conductingadhesive film 703 is a diamondoid-containing polymeric film, in whichsubstituent groups are attached either to the diamondoid nucleithemselves, or to other portions of the polymer, such that adhesion isfacilitated. An exemplary functional group that may be incorporated intoa diamondoid-containing film to facilitate adhesion is a carboxyl group.Such a device configuration is contemplated to be useful in a variety ofapplications in microelectronics and nanotechnology. Of course, it willbe appreciated by those skilled in the art that the surface 706 of body701 and surface 707 of body 702, in other words, the two surfaces being“glued” together, do not have to comprise smooth surfaces 706, 707, andin some embodiments of the present invention, a flexiblediamondoid-containing adhesive film is well-suited to adhereirregularly-shaped materials one to another, such as the rough surfacesdepicted at 708, 709.

[0127] An additional exemplary use of a diamondoid-containing materialhaving thermally conductive and electrically insulating properties is athermoelectric cooling device. It is known in the art that CMOS logicdevices operate significantly faster at low temperatures. Efforts havebeen made in the past to reduce the temperature at which amicroelectronic device is operated, including methods that includethermoelectric devices.

[0128] An exemplary microelectronics application in which a film that isboth thermally conducting and electrically insulating may be useful isthe thermoelectric device shown generally at 800 in FIG. 8. Thethermoelectric device 800 has an element 801 whose purpose is to pumpheat from a cold substrate 802 to a hot substrate 803. Thethermoelectric element 801 operates in a conventional manner bysupplying DC power from a supply 804 to provide a potential differenceacross the junction of two dissimilar materials, which may besemiconductors. In FIG. 8, the potential is applied between points 805and 806. The temperature of substrate 803 is at a high temperature, forexample, T_(high), whereas the temperature of substrate 802 is at alow-temperature, for example, T_(low). The purpose of the thermoelectricdevice 801 is to remove heat from the substrate at the low-temperature802 in a thermally “uphill” manner to substrate 803.

[0129] The thermal conductivity of the thermoelectric device 800 dependsin part upon the characteristics of the element 801, as well as thethermal conductivites of substrates 802 and 803. Any resistance to thetransfer of heat from substrate 802 to substrate 803 reduces theefficiency at which the device 800 operates. According to one embodimentof the present invention, the efficiency of the device 800 may beenhanced by providing a thermally conducting layer 802A adjacent to aheat sink layer 802B. Likewise, the substrate 803 may comprise athermally conducting layer 803A positioned adjacent to a heat sink layer803B. The enhanced level of thermal conductivity of the layers 802A and803A reduces the thermal resistance for removing heat from the systemvia the substrates 802 and 803, respectively. In an embodiment of thepresent invention, the thermally-conducting layers 802A and 803A maycomprise any of the material discussed above, such as as a polymerizeddiamondoid film, a diamondoid-containing ceramic and/or ceramiccomposite, a CVD deposited diamondoid-containing film, a CVD diamondfilm nucleated by diamondoids, or a diamondoid-containing film depositedby self-assembly techniques. In a preferred embodiment, however, thethermally-conducting layers 802A and 803A comprise adiamondoid-containing polymer film or a diamondoid-containing ceramic.

[0130] Referring again to FIG. 8, thermally conducting layers 802A and803A are electrically insulating as well in order to provide electricalisolation of the thermoelectric device 800. It will be obvious to thoseskilled in the art that if the layers 802A and 803A are not sufficientlyelectrically insulating, then the potential difference across element801 attempted by the supply 804 may be less than not desired, as well asunreliable or nonuniform. The electrical insulation and thermalconduction properties of diamondoid films suggest a utility inmicroelectronic applications such as thermoelectric device 800 whereboth properties are simultaneously desired.

[0131] In one embodiment of the present invention, the thermalconductivity of the material used in the above mentionned applicationsis at least 200 W/m K. In a preferred embodiment of the invention, thethermal conductivity of the material is at least 500 W/m K. In an evenmore preferred embodiment of the present invention, the thermalconductivity of the material is at least 1,000 W/m K.

[0132] An example of an application in which electrical insulation of adiamondoid-containing material is the property of greatest interestrelates to so-called back-end processing of an integrated circuitdevice. As transistor sizes in ultra large-scale integrated circuits aredecreased, it is desirable to reduce the capacitance of the metalinterconnection lines to each other to minimize the delays of electricalsignals conducted by the metal interconnection lines, as well as toreduce “crosstalk” between the lines. This permits the integratedcircuit to maintain or possibly even increase clock speed as the size ofthe component transistors are reduced.

[0133] One method for reducing the capacitance between interconnectionlines is to deposit a polymeric or other insulating material on theintegrated circuit chip between the metal interconnection lines wherethe polymeric or insulating material has a lower dielectric constant (k)then the conventionally used silicon dioxide (SiO₂). Silicon dioxide hasa dielectric constant of about 3.9 to 4.0. Efforts have been made toreplace silicon dioxide with a material having a dielectric constantlower than about 4.0 and these materials include, for example, thefluorinated oxides which have a dielectric constant of about 3.5.Fluorinated oxides are sometimes described by the acronym FSG, or by thesymbols SiOF and F_(x)SiO_(y). There are a variety of othersilicon-containing low-k materials that are not a fluorinated version ofthe conventionally used silicon dioxide. Carbon-doped glass, or SiOC,has a dielectric constant of about 2.5 to 3.1. The polysiloxanes HSQ,hydrogen silsesquioxane (HSiO_(3/2))_(n) and MSSQ, methyl silsesquioxane(CH₃SiO_(1.5))_(n) have dielectric constants in the range 2.3 to 3.0.These materials are sometimes referred to as spin-on dielectrics(SOD's), or flowable oxides FOx (Dow Corning). Finally, there are low-kdielectric materials that cannot contain silicon, and in fact are eitherpurely organic or substantially organic. Fluorinated amorphous carbon(FLAC, or α-CF), has a dielectric constant in the range 2.3 to 2.7.Polymeric materials include fluorinated poly(arylene ether) (FLARE,Allied Signal), fluorinated polyimide (DuPont), parylene,polyphenylquinoxaline (PPQ), benzocyclobutene (BCB), and the like.Members of this latter group of purely or substantially organicmaterials have dielectric constants in the range of about 2.0 to 3.0.

[0134] During back-end processing, that is to say, when theinterconnection system is constructed, a problem may occur when siliconbased low-k dielectric materials are etched in the presence of oxygen.Such low-k materials containing silicon may be more sensitive to oxygenthan the purely organic low-k materials. Oxidation of either HSQ or MSSQconverts Si—H bonds to Si—OH bonds, which causes the material to absorbmoisture, and experience an increase in the dielectric constant. Thus,it is advantageous to provide a low-k material for back end processingthat is substantially organic and that does not contain silicon as anelement.

[0135] In an article written by E. Korczynski entitled “Low-k dielectriccosts for dual-damascene integration,” Solid State Technology, May 1999,pp. 43-51, it is pointed out that in a fluorinated amorphous carbonfilm, variously called FLAC, α-CF, and CF_(x), which may be produced byconventional CVD techniques, that by controlling the fluorine to carbonratio in the precursor gases, as well as plasma parameters, theformation of electrically conductive C═C bonds having an sp²hybridization may be eliminated, leading to a film with a lower (andtherefore more desirable) dielectric constant. Furthermore, it is knownin the art to provide a porous version of a low-k dielectric material inorder to achieve a dielectric constant less than about 2(polytetrafluoroethylene, with a dielectric constant of about 2.1, isabout the best achieved so far). This is because a porous dielectricmaterial may be thought of as a composite where the dielectric constantof the air gaps (1.0) reduces the average and the overall dielectricconstant of the material as a whole. Thus, it is desirable to provide amaterial for use in back-end integrated circuit processing that has 1)porosity in the form of air gaps, 2) strong and rigid mechanicalproperties, 3) predominantly sp³ carbon carbon bonding, and optionally4) some degree of fluorine content.

[0136] In one embodiment of the present invention, a diamondoidcontaining material may be used for the low-k layers associated withintegrated circuit multilevel interconnection schemes. An exemplaryintegrated circuit for which a diamondoid-containing low-k dielectriclayer is suitable is shown schematically in FIG. 9A. This exemplaryintegrated circuit is a member of the CMOS technology family(complementary metal oxide semiconductor), where an NMOS(N-type metaloxide semiconductor) device is shown on the right and a PMOS(P-typemetal oxide semiconductor) device is shown on the left. A boronimplanted p-type silicon substrate 901 has a PMOS transistor showngenerally at 902 fabricated and in n-well 903 of the silicon substrate901. An NMOS transistor 904 has been fabricated in a p-well 905.

[0137] After the transistors have been fabricated on (actually in) thesurface of the silicon substrate 901, “back-end processing” occurs toconstruct the interconnection system that connects individualtransistors, such as the CMOS transistor 902 and the NMOS transistor904. Two levels of metal interconnect lines are shown: the first levelat 906 and the second level at 907. Metallic vias 908 and 909 serve tovertically connect the upper interconnection level 907 with the lowerinterconnection level 906. As it will be appreciated by those skilled inthe art, a dielectric layer or electrically insulating layer will bedeposited to isolate the interconnect lines located at any one levelfrom one another, as well as from interconnection lines or transistorelectrode leads from one another and from interconnection lines. Forexample, low-k dielectric layer 910 insulates interconnection lines atthe 906 level from the leads of the 902, 904 transistors. Low-kdielectric layer 911 insulates interconnection lines located at the 906level from one another, as well as from the interconnect lines locatedat the 907 level. Additionally, the low-k dielectric layer 911 isolatesthe vias 908, 909 from one another.

[0138] According to embodiments of the present invention, the low-kdielectric layers 910, 911 may comprise any of the diamondoid containingmaterials discussed above, including a polymerized diamondoid film, adiamondoid-containing ceramic and/or ceramic composite, a CVD depositeddiamondoid-containing film, a CVD diamond film nucleated by diamondoids,or a diamondoid-containing film deposited by self-assembly techniques.In a preferred embodiment, however, the low-k dielectric layers 910, 911comprise a diamondoid-containing polymeric film, which may be a polymersuch as a polyamide or a polyaryl ether. In this embodiment, thediamondoid-polyimide film of FIG. 2C may be used. The polyimide portionof the copolymer illustrated in FIG. 2C may be a fluorinated polyimide,and the diamondoid containing portion of the polymer may containfluorine substituents. Additionally, a diamondoid-containing materialwhich is suitable for low-k dielectric layers 910, 911 may contain airgaps 239 for reducing the overall dielectric constant of the material.As discussed previously, these air gaps 239 may be formed by the sterichindrance created with a large number of diamondoid groups spacedclosely together either within the main chain of the polymer or presentas side groups on the main chain of the polymer. The low-k dielectriclayers 910, 911 may be deposited by conventional spin coatingtechniques, or by CVD methods. In some embodiments, ether linkages suchas those depicted at reference numeral 234, 235 may be desirable toimpact flexibility into the main chain, and facilitate the processing ofthe layer.

[0139] According to embodiments of the present invention, the low-kdielectric layers 910, 911 has a dielectric constant of less than about4. In a preferred embodiment of the present invention, the dielectricconstant of the material is less than about 3. In an even more preferredembodiment of the present invention, the dielectric constant of thematerial is less than about two.

[0140] Integrated circuits such as those shown schematically in FIG. 9may have a top passivation layer 912 that serves to mechanically protectthe chip from environmental stresses and destructive conditions. Inanother embodiment of the present invention, the passivation layer 912may comprise a diamondoid-containing material of the types discussedabove, including a polymerized diamondoid film, a diamondoid-containingceramic and/or ceramic composite, a CVD deposited diamondoid-containingfilm, a CVD diamond film nucleated by diamondoids, or adiamondoid-containing film deposited by self-assembly techniques. Thediamondoid comprising the IC passivation layer may comprise aderivatized or underivatized diamondoid, and it may be either a higheror lower diamondoid, and/or combinations thereof. If the diamondoid ofthe passivation layer comprises a higher diamondoid, that diamondoid maybe selected from the group consisting of tetramantane, pentamantane,hexamantane, heptamantane, octamantane, nonamantane, decamantane, andundecamantane.

[0141] In an alternative embodiment, the diamondoid-containing materialsdiscussed above may be used in the dielectric layer of a capacitor,specifically, a capacitor for a static and/or dynamic random accessmemory (SRAM and DRAM, respectively). The capacitor will generally beconfigured as a first and second electrodes with the dielectric layerpositioned between the electrodes. In one embodiment, the diamondoid ofthe diamondoid-containing capacitor dielectric material comprises aderivatized diamondoid; in another embodiment the diamondoid may beunderivatized. The diamondoid may be a higher diamondoid or a lowerdiamondoid, or combinations thereof. If the capacitor dielectric layercomprises a higher diamondoid, the higher diamondoid may betetramantane, pentamantane, hexamantane, heptamantane, octamantane,nonamantane, decamantane, or undecamantane, and combinations thereof.

[0142] In a final embodiment of the present invention, a diamondoid ordiamondoid containing material is utilized as a cold cathode filament ina field emission device suitable for use, among other places, in flatpanel displays. The unique properties of a diamondoid make thispossible. These properties include the negative electron affinity of ahydrogenated diamond surface, in conjunction with the small size of atypical higher diamondoid molecule. The latter presents strikingelectronic features in the sense that the diamond material in the centerof the diamondoid comprises high purity diamond single crystal, with theexistence of significantly different electronic states at the surface ofthe diamondoid. These surface states may make possible very longdiffusion lengths for conduction band electrons.

[0143] In a chapter entitled “Novel Cold Cathode Materials,” in VacuumMicro-electronics (Wiley, New York, 2001), pp. 247-287, written by W.Zhu et al., the current requirements for a microtip field emitter arrayare given, as well as the properties an improved field emission cathodeare expected to deliver. Perhaps the most difficult problem presented bya conventional field emission cathode is the high voltage that must beapplied to the device in order to extract electrons from the filament.Zhu et al. report a typical control voltage for microtip field emitterarray of about 50-100 volts because of the high work function of thematerial typically comprising a field emission cathode. Diamonds ingeneral, and in particular a hydrogenated diamond surface, offer aunique solution to this problem because of the fact that a diamondsurface displays an electron affinity that is negative.

[0144] The electron affinity of the material is a function of electronicstates at the surface of the material. When a diamond surface ispassivated with hydrogen, that is to say, each of the carbon atoms onthe surface are sp³-hybridized, i.e., bonded to hydrogen atoms, theelectron affinity of that hydrogenated diamond surface surface canbecome negative. The remarkable consequence of a surface having anegative electron affinity is that the energy barrier to an electronattempting to escape the material is energetically favorable and in a“downhill” direction. Diamond is the only known material to have anegative electron affinity in air.

[0145] In more specific terms, the electron affinity χ of a material isnegative, where χ is defined to be the energy required to excite anelectron from an electronic state at the minimum of the conduction bandto the energy level of a vacuum. For most semiconductors, the minimum ofthe conduction band is below that of the vacuum level, so that theelectron affinity of that material is positive. Electrons in theconduction band of such a material are bound to the semiconductor by anenergy that is equal to the the electron affinity, and this energy mustbe supplied to the semiconductor to excite and electron from the surfaceof that material.

[0146] It should be noted that a field emission cathode comprising adiamond filament may suffer from an inherent property: while electronsin the conduction band are easily ejected into the vacuum level,exciting electrons from the valence band into the conduction band tomake them available for field emission may be problematic. This isbecause of the wide bandgap of diamond. In a normal situation, fewelectrons are able to traverse the bandgap, in other words, move fromelectronic states in the valence band to electronic states in theconduction band. Thus, diamond is generally thought to be unable tosustain electron emission because of its insulating nature. Toreiterate, although electrons may easily escape into the vacuum from thesurface of a hydrogenated diamond film, due to the negative electronaffinity of that surface, the problem is that there are no readilyavailable mechanisms by which electrons may be excited from the bulkinto electronic surface states.

[0147] There may be several ways to circumvent this problem.Observations of electron emission from diamond surfaces have either: 1)a high defect density, such as a relatively large inclusion of elementalnitrogen, or 2) an unusual microstructure including vapor-depositedislands or a film having a nanocrystalline morphology. They can alsodemonstrate quantum mechanically tunneling. It is known in the art thatdiamond materials with small grain sizes and high defect densitiesgenerally emit electrons more easily than diamond materials with largecrystalline sizes and low defect defect concentrations. It has beenreported (see the Zhu reference above) that outstanding emissionproperties are seen in ultrafine diamond powders containing crystalliteshaving sizes in the range of 1 to 20 nm. Emission of electrons has beenfound to originate from sites that are associated with defect structuresin diamond, rather than sharp features associated with the surface, andthat compared with conventional silicon or metal microtip emitters,diamond emitters show lower threshold fields, improved emissionstability, and robustness and vacuum environments.

[0148] According to embodiments of the present invention, a fieldemission cathode comprises a diamondoid, a derivatized diamondoid, apolymerized diamondoid, and all or any of the other diamondoidcontaining materials discussed in previous sections of this description.An exemplary field emission cathode comprising a diamondoid is shown inFIG. 10.

[0149] Referring to FIG. 10, a field emission device shown generally at1000 comprises a diamondoid filament 1001, which acts as a cathode forthe device 1000, and a faceplate 1002 on which a phosphorescent coating1003 has been deposited. The anode for the device may be either aconductive layer 1004 positioned behind the phosphorescent coating 1003,or an electrode 1005 positioned adjacent to the filament 1001. Duringoperation, a voltage from a power supply 1006 is applied between thefilament electrode 1007, and the anode of the device, either electrode1004 or 1005. A typical operating voltage (that is, the potentialdifference between the cathode and the anode) is less than about 10volts. This is what allows the cathode to be operated in a so-called“cold” configuration. A typical electronic affinity for a diamondoidsurface is contemplated to be less than about 3 eV, and in otherembodiments it may be negative. An electron affinity that is less thanabout 3 eV is considered to be a “low positive value.”

[0150] Although a diamond material is generally thought to beelectrically insulating, the diamondoid filament 1001 may be smallenough to allow electrons to tunnel (in a quantum mechanical sense) fromthe filament electrode 1007 to an opposite surface of the diamondoid,which may be the surface 1008 or the tip 1009. It will be appreciated bythe skilled in the art that it is not essential for the diamondoidfilament 1001 to have an apex or tip 1009, since the surface of thediamondoid is hydrogenated and sp³-hybridized. In an alternativeembodiment, the surface of the cathode may comprise adiamondoid-containing material that is at least partially derivatizedsuch that the surface comprises both sp² and sp³-hybridization.

[0151] An advantage of this embodiment of the present invention is thatmuch greater resolution of the device may be realized relative to aconventional field emission device because of the small size of atypical diamondoid, derivatized diamondoid, self-assembled diamondoidstructure, or diamondoid aggregate.

[0152] Many modifications of the exemplary embodiments of the inventiondisclosed above will readily occur to those skilled in the art.Accordingly, the invention is to be construed as including all structureand methods that fall within the scope of the appended claims.

1-60. (Canceled)
 61. A capacitor having a dielectric layer positionedbetween a first electrode and a second electrode, wherein the dielectriclayer comprises a lower diamondoid-containing polymerized material, andwherein the lower diamondoid is triamantane.
 62. A capacitor having adielectric layer positioned between a first electrode and a secondelectrode, wherein the dielectric layer comprises a lowerdiamondoid-containing material selected from the group consisting of alower diamondoid-containing sintered ceramic, a lower diamondoid ceramiccomposite, and a self-assembled lower diamondoid film.
 63. The capacitorof claim 62, wherein the lower diamondoid is selected from the groupconsisting of adamantane, diamantane, and triamantane.
 64. A capacitorhaving a dielectric layer positioned between a first electrode and asecond electrode, wherein the dielectric layer comprises a higherdiamondoid-containing material.
 65. The capacitor of claim 64, whereinthe higher diamondoid of the higher diamondoid-containing material isselected from the group consisting of tetramantane, pentamantane,hexamantane, heptamantane, octamantane, nonamantane, decamantane, andundecamantane.
 66. The capacitor of claim 64, wherein the higherdiamondoid-containing material is selected from the group consisting ofa higher diamondoid-containing polymer, a higher diamondoid-containingsintered ceramic, a higher diamondoid ceramic composite, a CVD higherdiamondoid film, and a self-assembled higher diamondoid film.
 67. Acapacitor having a dielectric layer positioned between a first electrodeand a second electrode, wherein the dielectric layer is adiamondoid-containing material comprising a mixture of lower and higherdiamondoids, wherein the lower diamondoid is selected from the groupconsisting of adamantane, diamantane, and triamantane, and wherein thehigher diamondoid is selected from the group consisting of tetramantane,pentamantane, hexamantane, heptamantane, octamantane, nonamantane,decamantane, and undecamantane.
 68. The capacitor of claim 67, whereinthe diamondoid-containing material is selected from the group consistingof a diamondoid-containing polymer, a diamondoid-containing sinteredceramic, a diamondoid ceramic composite, a CVD diamondoid film, and aself-assembled diamondoid film.
 69. The capacitor of claim 61, whereinthe capacitor is a part of a random access memory device.
 70. Thecapacitor of claim 62, wherein the capacitor is a part of a randomaccess memory device.
 71. The capacitor of claim 64, wherein thecapacitor is a part of a random access memory device.
 72. The capacitorof claim 67, wherein the capacitor is a part of a random access memorydevice.